Reduction of Oxygen 



231 



Wright has given the most simple modification by suggest- 

 ing that the cotton stopper of the ordinary culture-tube 

 have its projecting part cut off 

 and the plug itself pushed down 

 the tube for a short distance. 

 Some alkaline pyro gallic acid so- 

 lution is poured upon the cotton, 

 to saturate it, and the tube 

 tightly corked. 



Hiss has also adopted the 

 method so as to be very satis- 

 factory for use with Petri dishes. 

 The dishes selected should be 

 rather deeper than ordinary. 

 They are sterilized and inocu- 

 lated in the ordinary manner and 

 then inverted. The dish is cau- 

 tiously raised, and some pyro- 

 gallic acid carefully poured into 

 the lid and the dish gently 

 dropped into place again. The 

 alkaline solution is then poured 

 into the crevice between the 

 edges of the dish and the lid, 

 and then the remainder of the 

 space filled with melted albolene. 

 When these dishes are carefully 

 stood away, the alkaline pyro- 

 gallic acid absorbs all of the con- 

 tained oxygen and the anaerobic 

 cultures develop quite well. ' The 

 growing colonies can be exam- 

 ined as often as may be necessary 

 through the bottom of the dishes, which must, of course, 

 always be kept in the inverted position. 



4. Reduction of Oxygen. Pasteur and, later, Roux 

 have recommended the cultivation of anaerobic bacteria in 

 association with aerobic bacteria by which the oxygen was 

 to be absorbed. This method is too crude to be employed 

 at the present time, as it destroys the essential character- 

 istics of the cultures by mixing the products of the bacteria. 



Chemic reduction of the oxygen has been attempted by 

 the addition of 2 per cent, of glucose, as suggested by Libo- 



Fig. 56. Spirillum ru- 

 brum. Glucose agar slant 

 culture of five days. Abun- 

 dant production of pigment 

 on the surface. (The U tube 

 was soiled by the reducing 

 fluid during handling by the 

 photographer.) (Nichols and 

 Schmitter.) 



